Low free formaldehyde phenolic polyol formulation

ABSTRACT

A resin is prepared by the reaction of a phenol, an aldehyde and an aliphatic hydroxy compound containing two or more hydroxy groups per molecule in the presence of a divalent metal ion catalyst. These resins react with polyisocyanates to form polyurethanes that are useful binders for foundry cores and molds.

FIELD OF THE INVENTION

This invention relates to a method for preparing modified phenolicresole resins useful in binder compositions and to a process for makingfoundry cores and molds employing these binders. More particularly, theinvention relates to a multistep process which incorporates into theresin an aliphatic hydroxy compound which contains two or more hydroxygroups per molecule.

BACKGROUND OF THE INVENTION

Binders or binder systems for foundry cores and molds are well known. Inthe foundry art, cores or molds for making metal castings are normallyprepared from a mixture of an aggregate material, such as sand, and abinding amount of a binder system. Typically, after the aggregatematerial and binder have been mixed, the resultant mixture is rammed,blown or otherwise formed to the desired shape or patterns, and thencured with the use of catalyst and/or heat to a solid, cured state.

Resin binders used in the production of foundry molds and cores areoften cured at high temperatures to achieve the fast-curing cyclesrequired in foundries. However, in recent years, resin binders have beendeveloped which cure at a low temperature, to avoid the need forhigh-temperature curing operations which have higher energy requirementsand which often result in the production of undesirable fumes.

One group of processes which do not require heating in order to achievecuring of the resin binder are referred to as "cold-box" processes. Insuch processes, the binder components are coated on the aggregatematerial, such as sand, and the material is blown into a box of thedesired shape. Curing of the binder is carried out by passing a gaseouscatalyst at ambient temperatures through the molded resin-coatedmaterial. In such processes, the binder components normally comprise apolyhydroxy component and a polyisocyanate component. These cure to forma polyurethane in the presence of a gaseous amine catalyst.

Another group of binder systems which do not require gassing or heatingin order to bring out curing are known as "no-bake" systems. These"no-bake" systems also frequently employ an aggregate material, such assand coated with a polyhydroxy component and a polyisocyanate component.In this case, the coated sand is usually mixed with a liquid tertiaryamine catalyst just before the sand is placed into a holding pattern orcore box, and the material is allowed to cure at ambient temperatures orslightly higher.

Although developments in resinous binder systems which can be processedaccording to the "cold-box" or "no-bake" processes have resulted in theprovisions of useful systems, workers have continually sought to improvethe binders of these systems. One such improvement is disclosed in U.S.Pat. No. 4,546,124 issued on Oct. 8, 1985 to Laitar et al. This patent,which describes an alkoxy modified phenolic resole resin as thepolyhydroxy component of the polyurethane binder, is incorporated hereinby reference in its entirety.

Various other workers have disclosed techniques for modifying phenolicresins. However, none of these modified resins have been used ascomponents of binders for foundry cores and molds. For example, U.S.Pat. No. 2,376,213 discloses that water miscible phenolic resins can beprepared by the reaction of phenol with an excess of formaldehyde in thepresence of a polyhydroxy alcohol using an alkali metal hydroxide as acatalyst. On the other hand, U.S. Pat. No. 3,156,670 discloses theformation of a water insoluble liquid phenolic resin. The phenolicnuclei are said to be linked together by dihydric glycol residuesthrough aliphatic ether linkages. The reaction between the phenol,formaldehyde and the glycol is carried out using an alkaline catalystand then the reaction is completed by dehydration under acidicconditions.

Preparation of molding materials is disclosed in U.S. Pat. No.3,894,981. These are prepared by the reaction of phenol, an aldehyde,and a monohydric or dihydric alcohol in the presence of a filling agentsuch as wood flour or asbestos. The reaction is carried out under mildlyacidic anhydrous conditions at high temperatures. Another modifiedphenolic resin said to be useful for making resin impregnated filterpaper is disclosed in U.S. Pat. No. 4,150,194. It is prepared by thereaction of phenol with an aqueous aldehyde and a glycol in the presenceof an alkaline catalyst.

Three patents disclose modified phenolic resins which have been used tomake urethane foams. In U.S. Pat. No. 4,404,334, phenol, anhydrousformaldehyde and a glycol are reacted in the presence of zinc acetatecatalyst under nonrefluxing conditions. The products are said to beuseful to plasticize conventional phenolic resins or to prepare improvedheat and flame resistant polyurethane foams. U.S. Pat. Nos. 4,448,951and 4,473,669 disclose the reaction of phenol and nonaqueous aldehydeswith an alcohol or polyol in the presence of a divalent metal ioncatalyst. The products were used to make solid urethane foams of lowfriability and low combustibility.

All of the resole resins previously used to make urethane foundrybinders have possessed an undesirable formaldehyde odor. The release ofappreciable quantities of formaldehyde into the atmosphere isundesirable from an environmental view point. Previous attempts toreduce the amount free formaldehyde in the resin has required longperiods of heating and has produced resins of undesirably highviscosity.

We have now discovered a process whereby modified resole resins can beprepared which emit little formaldehyde and yet retain their desiredrange of viscosity. These resins can be used to make urethane bindersparticularly suitable for use in the "cold-box" and "no-bake" processes.Furthermore, when the resins are combined with polyisocyanates for usein the "cold-box" process, they give a mixture with better bench lifethan ones prepared with resole resins previously employed.

SUMMARY OF THE INVENTION

In accordance with this invention, there is provided a method forpreparing a modified orthobenzylic ether-containing resole resin whichcomprises the steps:

(a) reacting a phenol in the presence of a divalent metal ion catalystat a pH below about 7 with a molar excess of an aqueous aldehyde;

(b) adding to the reaction mixture of step (a) from about 0.001 to about0.03 mole of an aliphatic hydroxy compound per mole of phenol when from0% to about 85% of the aldehyde has reacted;

(c) reacting the mixture of step (b) until from about 80% to about 98%of the aldehyde has reacted; and

(d) heating the reaction mixture of step (c) under vacuum until theamount of free formaldehyde in the mixture is less than about 1% byweight,

wherein the aliphatic hydroxy compound added in step (b) contains two ormore hydroxy groups per molecule and has a hydroxyl number of from about200 to about 1850.

Further provided, in accordance with this invention, is a method forpreparing a modified orthobenzylic ether-containing resole resin whichcomprises the steps:

(a) reacting a phenol in the presence of a divalent metal ion catalystat a pH below about 7 with a molar excess of an aqueous aldehyde and atleast about 0.25 mole of a monohydric alcohol per mole of phenol;

(b) adding to the reaction mixture of step (a) from about 0.001 to about0.03 mole of an aliphatic hydroxy compound per mole of phenol when from0% to about 85% of the aldehyde- has reacted;

(c) reacting the mixture of step (b) until from about 80% to about 98%of the aldehyde has reacted; and

(d) heating the reaction mixture of step (c) under vacuum until theamount of free formaldehyde in the mixture is less than about 1% byweight,

wherein the aliphatic hydroxy compound added in step (b) contains two ormore hydroxy groups per molecule and has a hydroxyl number of from about200 t about 1850.

Further, in accordance with the invention, there is provided a bindercomposition comprising a mixture of a phenolic resin component, anisocyanate component selected from diisocyanates and polyisocyanates andsufficient catalyst to catalyze the reaction between the phenolic resincomponent and the isocyanate component wherein the phenolic resincomponent is a modified orthobenzylic ether-containing resole resinwhich has covalently bound into the resin an aliphatic hydroxy compoundwhich contains two or more hydroxy groups per molecule and has a hydroxynumber of from about 200 to about 1850.

Finally, in accordance with the invention, there is provided a processfor making foundry cores or molds which comprises admixing aggregatematerial, such as a foundry sand or the like, and a binding amount of abinder composition comprising a phenolic resin component, an isocyanatecomponent selected from diisocyanates and polyisocyanates and sufficientcatalyst to catalyze the reaction between the phenolic resin componentand the isocyanate component wherein the phenolic resin component is amodified orthobenzylic ether-containing resole resin which hascovalently bound into the resin an aliphatic hydroxy compound whichcontains two or more hydroxy groups per molecule and has a hydroxynumber of from about 200 to about 1850.

DETAILED DESCRIPTION OF THE INVENTION

The modified orthobenzylic ether-containing resole resin prepared by themethod of this invention is prepared by the reaction of a phenol and analdehyde in the presence of an aliphatic hydroxy compound containing twoor more hydroxy groups per molecule. In one preferred modification ofthe process, the reaction is also carried out in the presence of amonohydric alcohol.

Phenols suitable for preparing the modified phenolic resole resins ofthis invention are generally any of the phenols which may be utilized inthe formation of phenolic resins, and include substituted phenols, aswell as unsubstituted phenol per se. The nature of the substituent canvary widely, and exemplary substituted phenols include alkyl-substitutedphenols, aryl-substituted phenols, cycloakyl-substituted phenols,alkenyl-substituted phenols, alkoxy-substituted phenols,aryloxy-substituted phenols and halogen-substituted phenols. Specificsuitable exemplary phenols include in addition to phenol per se,o-cresol, m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 3,4,5-trimethylphenol, 3-ethyl phenol, 3,5-diethyl phenol, p-butyl phenol, 3,5-dibutylphenol, p-amyl phenol, p-cyclohexyl phenol, p-octyl phenol,3,5-dicyclohexyl phenol, p-phenyl phenol, p-crotyl phenol, 3,5-dimethoxyphenol, 3,4,5-trimethoxy phenol, p-ethoxy phenol, p-butoxy phenol,3-methyl-4-methoxy phenol, and p-phenoxy phenol. A preferred phenoliccompound is phenol itself.

The aldehyde employed in the formation of the modified phenolic resoleresins of this invention can also vary widely. Suitable aldehydesinclude any of the aldehydes previously employed in the formation ofphenolic resins, such as formaldehyde, acetaldehyde, propionaldehyde andbenzaldehyde. In general, the aldehydes employed contain from 1 to 8carbon atoms. The most preferred aldehyde is an aqueous solution offormaldehyde.

Metal ion catalysts useful in production of the modified phenolic resoleresins of the present invention include salts of the divalent ions ofMn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca, and Ba. Tetraalkoxy titaniumcompounds of the formula Ti(OR)₄ where R is an alkyl group containingfrom 3 to 8 carbon atoms, are also useful catalysts for this reaction. Apreferred catalyst is zinc acetate. These catalysts give phenolic resoleresins wherein the preponderance of the bridges joining the phenolicnuclei are ortho-ortho benzylic ether bridges of the general formula--CH₂ (OCH₂)_(n) --where n is a small positive integer.

A molar excess of aldehyde per mole of phenol is used to make the resoleresins of this invention. It is preferable that the molar ratio ofaldehyde to phenol be in the range of from about 1.1:1 to about 2.2:1.

In the practice of this invention, the phenol and aldehyde are reactedin the presence of the divalent metal ion catalyst at a pH below about7. A convenient way to carry out the reaction is by heating the mixtureunder reflux conditions. Reflux, however, is not required.

To the reaction mixture is added an aliphatic hydroxy compound whichcontains two or more hydroxy groups per molecule. The hydroxy compoundis added at a molar ratio of hydroxy compound to phenol of from about0.001:1 to about 0.03:1. This hydroxy compound may be added to thephenol and aldehyde reaction mixture at any time when from 0% (i.e., atthe start of the reaction) to when about 85% of the aldehyde hasreacted. It is preferred to add the hydroxy compound to the reactionmixture when from about 50% to about 80% of the aldehyde has reacted.

Useful hydroxy compounds which contain two or more hydroxy groups permolecule are those having a hydroxyl number of from about 200 to about1850. The hydroxyl number is determined by the standard acetic anhydridemethod and is expressed in terms of mg KOH/g of hydroxy compound.Suitable hydroxy compounds include ethylene glycol, propylene glycol,1,3-propanediol, diethylene glycol, triethylene glycol, glycerol,sorbitol and polyether polyols having hydroxyl numbers greater thanabout 200. Glycerol is a particularly suitable hydroxy compound for usein the process of this invention.

After the aliphatic hydroxy compound containing two or more hydroxygroups per molecule is added to the reaction mixture, heating iscontinued until from about 80% to about 98% of the aldehyde has reacted.Although the reaction can be carried out under reflux until about 98% ofthe aldehyde has reacted, prolonged heating is required and it ispreferred to continue the heating only until about 80% to 90% of thealdehyde has reacted. At this point, the reaction mixture is heatedunder vacuum at a pressure of about 50 mm of Hg until the freeformaldehyde in the mixture is less than about 1%. Preferably, thereaction is carried out at 95° C. until the free formaldehyde is lessthan about 0.1% by weight of the mixture. The catalyst may beprecipitated from the reaction mixture before the vacuum heating step ifdesired. Citric acid may be used for this purpose.

In one preferred modification of the method of preparing a modifiedorthobenzylic ether-containing resole resin of this invention, thereaction mixture also contains at least about 0.25 mole of a monohydricalcohol per mole of phenol. The alcohol may be any primary or secondarymonohydric aliphatic alcohol containing from 1 to 8 carbon atoms.Examples of useful alcohols are methanol, ethanol, n-propanol,isopropanol, n-butanol and hexanol. Methanol is a preferred alcohol. Themonohydric alcohol is generally added to the reaction mixture of phenoland aqueous aldehyde at the start of the reaction. However, it may beadded at a later point in the reaction if desired. Use of at least about0.25 mole of alcohol per mole of phenol will generally provide thedesired degree of substitution. Although higher molar ratios of alcoholto phenol may be employed, the presence of a large amount of alcoholtends to slow down the reaction between the phenol and the aldehyde andleave considerable amounts of unreacted alcohol to be evaporated a theend of the reaction.

As noted above, the modified orthobenzylic ether-containing resoleresins prepared by the method of this invention can be used to preparebinder compositions. Such compositions comprise a mixture of thephenolic resin component, an isocyanate component selected fromdiisocyanates and polyisocyanates and sufficient catalyst to catalyzethe reaction between the phenolic resin component and the isocyanatecomponent.

The isocyanate component which can be employed in a binder according tothis invention may vary widely and has a functionality of 2 or more.Exemplary of the useful isocyanates are organic polyisocyanates such astolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, and mixturesthereof, and particularly the crude mixtures thereof that arecommercially available. Other typical polyisocyanates includemethylene-bis-(4-phenyl isocyanate), n-hexyl diisocyanate,naphthalene-1,5-diisocyanate, cyclopentylene-1,3-diisocyanate,p-phenylene diisocyanate, tolylene-2,4,6-triisocyanate, andtriphenylmethane-4,4',4"-triisocyanate. Higher isocyanates are providedby the liquid reaction products of (1) diisocyanates and (2) polyols orpolyamines and the like. In addition, isothiocyanates and mixtures ofisocyanates can be employed. Also contemplated are the many impure orcrude polyisocyanates that are commercially available. Especiallypreferred for use in the invention are the polyaryl polyisocyanateshaving the following general formula: ##STR1## wherein R is selectedfrom the group consisting of hydrogen, chlorine, bromine, alkyl groupshaving 1 to 5 carbon atoms; X is selected from the group consisting ofhydrogen, alkyl groups having 1 to 10 carbon atoms and phenyl; and n hasan average value of at least about 1 and generally about 1 to about 3.The preferred polyisocyanate may vary with the particular system inwhich the binder is employed.

Generally, the amounts of the phenolic component and the isocyanatecomponent employed in a binder composition of the invention are notcritical and can vary widely. However, there should at least be enoughof the isocyanate component present to give adequate curing of thebinder.

The isocyanate component is generally employed in a range of from about15% to about 400% by weight, based on the weight of the phenoliccomponent, and is preferably employed in a range of from about 20 toabout 200%. Moreover, a liquid isocyanate can be used in undiluted form,so long as there is sufficient solvent employed with the phenoliccomponent, solid or viscous isocyanates can also be utilized and aregenerally used with an organic solvent. In this respect, the isocyanatecomponent may include up to 80% by weight of solvent.

Furthermore, it is to be understood that in accordance with theinvention, both the phenolic and isocyanate components are, as apractical matter, preferably dissolved in solvents in order to providecomponent solvent mixtures of desirable viscosity and thus facilitatethe use of the same, such as in coating aggregate material with thecomponents. In this respect, sufficient solvents are employed to providea Brookfield viscosity of solutions of the components which is belowabout 1000 centipoises (cps) and preferably less than about 500centipoises. More specifically, while the total amount of solvent canvary widely, it is generally present in a composition of this inventionin a range of from about 5% to about 70% by weight, based on totalweight of the polyhydroxy component, and is preferably present in arange of from about 20% to about 60% by weight.

The solvents employed in the practice of this invention are generallymixtures of hydrocarbon and polar organic solvents such as organicesters.

Suitable exemplary hydrocarbon solvents include aromatic hydrocarbonssuch as benzene, toluene, xylene, ethyl benzene, high boiling aromatichydrocarbon mixtures, heavy aromatic naphthas and the like. It ispreferred to use hydrocarbon solvents with a flash point about 100° F.

As previously indicated hereinabove, the compositions of this inventioncan be cured by both the "cold-box" and "no-bake" processes. Thecompositions are cured by means of a suitable catalyst. While anysuitable catalyst for catalyzing the reaction between the phenolic resincomponent and isocyanate component may be used, it is to be understoodthat when employing the "cold-box" process, the catalyst employed isgenerally a volatile catalyst. On the other hand, where the "no-bake"process is employed, a liquid catalyst is generally utilized. Moreover,no matter which process is utilized, that is, the "cold-box" or the"no-bake" process, at least enough catalyst is employed to causesubstantially complete reaction of the polyhydroxy and isocyanatecomponent.

Preferred exemplary catalysts employed when curing the compositions ofthis invention by the "cold-box" process are volatile tertiary aminegases which are passed through a core or mold generally along with aninert carrier, such as air or carbon dioxide. Exemplary volatiletertiary amine catalysts which result in a rapid cure at ambienttemperature that may be employed in the practice of the presentinvention include trimethylamine, triethylamine and dimethylethylamineand the like.

On the other hand, when utilizing the compositions of this invention inthe "no-bake" process, liquid tertiary amine catalysts are generally andpreferably employed. Exemplary liquid tertiary amines which are basic innature include those having a pK_(b) value in a range of from about 4 toabout 11. The pK_(b) value is the negative logarithm of the dissociationconstant of the base and is a well-known measure of the basicity of abasic material. The higher the number is, the weaker the base. Basesfalling within the mentioned range are generally, organic compoundscontaining one or more nitrogen atoms. Preferred among such materialsare heterocyclic compounds containing at least one nitrogen atom in thering structure. Specific examples of bases which have a pK_(b) valuewithin the range mentioned include 4- alkylpyridines wherein the alkylgroup has from 1 to 4 carbon atoms, isoquinoline, arylpyridines, such asphenyl pyridine, pyridine, acridine, 2-methoxypyridine, pyridazines,3-chloropyridine, and quinoline, N-methylimidazole, N-vinylimidazole,4,4-dipyridine, phenylpropylpyridine, 1-methylbenzimidazole and1,4-thiazine. Additional exemplary, suitable preferred catalystsinclude, but are not limited to, tertiary amine catalysts such asN,N-dimethylbenzylamine, triethylamine, tribenzylamine,N,N-dimethyl-1,3-propanediamine, N,N-dimethylethanolamine andtriethanolamine. It is to be understood that various metal organiccompounds can also be utilized alone as catalysts or in combination withthe previously mentioned catalyst. Examples of useful metal organiccompounds which may be employed as added catalytic materials are cobaltnaphthenate, cobalt octoate, dibutyltin dilaurate, stannous octoate andlead naphthenate and the like. When used in combinations, such catalyticmaterials, that is the metal organic compounds and the amine catalysts,may be employed in all proportions with each other.

It is further understood that when utilizing the compositions of thisinvention in the "no-bake" process, the amine catalysts, if desired, canbe dissolved in suitable solvents such as, for example, the hydrocarbonsolvents mentioned hereinabove. The liquid amine catalysts are generallyemployed in a range of from about 0.5% to about 15% by weight, based onthe weight of the phenolic resin component present in a composition inaccordance with the invention.

When employing a binder composition of this invention in the "no-bake"process, the curing time can be controlled by varying the amount ofcatalyst added. In general, as the amount of catalyst is increased, thecure time decreases. Furthermore, curing takes place at ambienttemperature without the need for subjecting the compositions to heat, orgassing or the like. In this regard, however, in usual foundry practicepreheating of the sand is often employed to raise the temperature of thesand to from about 30° F. up to as high as 120° F. and preferably up toabout 75° F. to 100° F. in order to accelerate the reactions and controltemperature and thus provide a substantially uniform operatingtemperature on a day-to-day basis. However, it is to be understood thatsuch preheating is neither critical nor necessary in carrying out thepractice of this invention.

While the binder compositions of this invention may be employed byadmixing the same with a wide variety of particulate materials, such aslimestone, calcium silicate and gravel and the like, in order to bindthe same, and the admixture then manipulated in suitable fashion to formcoherent shaped structures, they are particularly useful in the foundryart as binding compositions for foundry sand. Suitable foundry sandsinclude silica, lake, zircon, chromite, olivine sands and the like. Whenso employed, the amount of binder and sand can vary widely and is notcritical. On the other hand, at least a binding amount of the bindingcomposition should be present in order to coat substantially, completelyand uniformly all of the sand particles and to provide a uniformadmixture of the sand and binder and, so that when the admixture isconveniently shaped as desired and cured, there is provided a strong,uniform, shaped article which is substantially uniformly curedthroughout, thus minimizing breakage and warpage during handling of theshaped article, such as, for example, sand molds or cores, so made. Inthis regard, the binder may be present in a moldable composition, inaccordance with this invention, in a range of from about 0.4% to about6.0% by weight based on the total weight of the composition.

In the practice of this invention, additives normally utilized infoundry manufacturing processes can also be added to the compositionsduring the sand coating procedure. Such additives include materials suchas iron oxide, clay, carbohydrates, potassium fluoroborates, wood flourand the like.

Other commonly employed additives can be optionally used in the bindercompositions of this invention. Such additives include, for example,organo silanes which are known coupling agents. The use of suchmaterials may enhance the adhesion of the binder to the aggregatematerial. Examples of useful coupling agents of this type include aminosilanes, epoxy silanes, mercapto silanes, hydroxy silanes and ureidosilanes.

In general, the process for making foundry cores and molds in accordancewith this invention comprises admixing aggregate material with at leasta binding amount of the modified phenolic resole resin component. Theresin is dissolved in sufficient solvent to reduce the viscosity of thephenolic resinous component to below about 1000 centipoises. Thissolvent comprises hydrocarbon solvents, polar organic solvents andmixtures thereof. Then, an isocyanate component, having a functionalityof two or more, is added and mixing is continued to uniformly coat theaggregate material with the phenolic resin and isocyanate components.The admixture is suitably manipulated, as for example, by distributingthe same in a suitable core box or pattern. A sufficient amount ofcatalyst is added to substantially and completely catalyze the reactionbetween the components. The admixture is cured forming a shaped product.

It is to be understood that there is no criticality in the order ofmixing the constituents with the aggregate material. On the other hand,the catalyst should generally be added to the mixture as the lastconstituent of the composition so that premature reaction between thecomponents does not take place. It is to be further understood that as apractical matter, the phenolic resin component can be stored separatelyand mixed with solvent just prior to use of or, if desirable, mixed withsolvent and stored until ready to use. Such is also true with theisocyanate component. On the other hand, as a practical matter, thephenolic and isocyanate components should not be brought into contactwith each other until ready to use in order to prevent any possiblepremature reaction between them. The components may be mixed with theaggregate material either simultaneously or one after the other insuitable mixing devices, such as mullers, continuous mixers, ribbonblenders and the like, while continuously stirring the admixture toinsure uniform coating of aggregate particles.

More specifically, however, when the admixture is to be cured accordingto "cold-box" procedures, the admixture after shaping as desired, issubjected to gassing with vapors of an amine catalyst. Sufficientcatalyst is passed through the shaped admixture to provide substantiallycomplete reaction between the components. The flow rate is dependent, ofcourse, on the size of the shaped admixture as well as the amount ofphenolic resin therein.

In contrast, however, when the admixture is to be cured according to"no-bake" procedures, the catalyst is generally added to the aggregatematerial with the phenolic and isocyanate components. The admixture isthen shaped and simply permitted to cure until reaction between thecomponents is substantially complete, thus forming a shaped product suchas a foundry core or mold. On the other hand, it is to be understoodthat the catalyst may also be admixed with either one of the componentsprior to coating of the aggregate material with the components.

Consequently, by so proceeding, as indicated with an admixture offoundry sand and a binding amount of the phenolic and isocyanatecomponents with the catalyst, there is formed a foundry core or moldcomprising foundry sand and a binding amount of a binder compositioncomprising the reaction product of the phenolic and isocyanatecomponents.

The following specific examples illustrate the present invention. Theyare not intended to limit the invention in any PG,24 way. Unlessotherwise indicated, all parts and percentages are by weight.

EXAMPLE 1

In a 5-liter flask equipped with a stirrer, reflux condensor andthermometer was placed 1325 g phenol, 1269 g of 50% aqueous formaldehydesolution, 359 g of methanol and 112 g of a 25% aqueous solution of zincacetate. Then, 31 g of glycerol was added and the contents were broughtto 95° C. and allowed to reflux until the free formaldehydeconcentration as measured by the standard hydroxylamine hydrochloridemethod was 2.5% by weight. At this point, the mixture was cooled to50°-60° C. and 10 g of citric acid was added to precipitate the metalcatalyst. The batch was then heated under full vacuum (50 mm of Hg) andallowed to react at 95° C. until the measured free formaldehyde was 0.1%by weight. Similar runs were carried out except that the glycerol wasadded to the reaction mixture at various times after the refluxing hadbegun. In one experiment, as a control, no glycerol was added. Theviscosities of the various solutions were measured at 25° C. using aBrookfield viscometer (Model RVF) with a number 7 spindle. The viscositywas also measured on the control resin (no glycerol added) to which 1.8%glycerol had been added after the resin was cooled to room temperature.The results are given in Table I.

In order to test the amount of formaldehyde in the head space above theliquid, solutions of each resin were prepared by dissolving 65 parts ofthe resin and 8 parts by weight of dibasic ester DBE-9 in 27 parts byweight of an aromatic hydrocarbon solvent containing 98% aromatics, 2%aliphatics and having a distillation range of 155°-173° C. Dibasic ester(DBE-9) available from DuPont, Wilmington, Del., contains approximately73% dimethylglutarate, 25% dimethylsuccinate and 1.5% dimethyladipate.Three grams of a solution to be measured was placed in a 35.1 ml vial(Fisher Scientific Catalog No. 03339-5C). A rubber stopper which fitsnugly into the top of the vial was modified to accommodate a 1/16 in.internal diameter by 3.25 in. long polyethylene tube and a 1/8 in.internal diameter tube. The smaller tube extended through the stopper sothat when the stopper was fitted into the vial, the one end of the tubewas one inch above the bottom of the vial and 5/8 in. above the sample.The other end of this tube was left free. The larger diameter tube wasconnected to an Interscan 4000 Series compact portable analyzer(Interscan Corp., Chatsworth, Calif.). The sample was drawn into theanalyzer through the 1/8 in. tube and room air replaced this volume byentering through the 1/16 in. tube. A stabilized reading was obtainedwithin two minutes of sampling. Tests were run at 23° C. and readingswere taken after five minutes of sampling. The readings, reported aspercentages of the amount of formaldehyde measured for the controlcontaining no glycerol, are also given in Table I.

Proton magnetic resonance spectra of the samples showed that thehydrogens on the primary hydroxyls of glycerol were no longer present inthe samples where the glycerol had been heated with the resins. Thisindicates that the glycerol is covalently bound into the resin.Carbon-13 spectra also indicate that the glycerol is fully incorporatedinto the resin. No incorporation of the glycerol was indicated when theglycerol was added to the cold resin.

The results given in Table I show that the resins containingincorporated glycerol have lower formaldehyde in the atmosphere abovethem and have lower viscosity than the control resin prepared withoutthe glycerol or a control resin containing glycerol which was notincorporated in the resin.

                  TABLE I                                                         ______________________________________                                        Properties Of Modified Resins Containing Glycerol                                    % Formalde-                                                            Resin  hyde When     Viscosity Head Space                                     No.    Glycerol Added                                                                              cps (25° C.)                                                                     Formaldehyde (%)                               ______________________________________                                        1      20.7 (Start)   96,800   50                                             2       9.9 (52% Reacted)                                                                           70,000   45                                             3       5.1 (75% Reacted)                                                                           60,000   23                                             4       4.2 (80% Reacted)                                                                          102,000   67                                             5       2.5 (88% Reacted)                                                                          109,200   27                                             6      (no glycerol) 128,000   100                                            (control)                                                                     7                    118,000   95                                             (con-                                                                         trol +                                                                        1.8%                                                                          glycerol                                                                      added                                                                         cold)                                                                         ______________________________________                                    

EXAMPLE 2

The general procedure of Example 1 was followed, except that otherpolyhydroxy compounds were substituted for glycerol. These compoundswere all added during the first stage of the reaction at a point wherethe free formaldehyde was about 10% by weight. They were then reacted inthe final stage to a free formaldehyde concentration of about 0.1%. Thefree formaldehyde in the head space, as well as the viscosity of theseresins, were measured by the same method used in Example 1. The resultsgiven in Table II show that, like glycerol, other polyhydroxy compoundsincorporated into the resin reduce the viscosity of the resin, as wellas the amount of formaldehyde in the atmosphere above the resin.

                  TABLE II                                                        ______________________________________                                        Properties Of Modified Resins                                                 Containing Polyhydroxy Compounds                                              Resin  Polyhydroxy   Viscosity Head Space                                     No.    Compound Added                                                                              cps (25° C.)                                                                     Formaldehyde (%)                               ______________________________________                                         8     polyether triol                                                                             34,000    56                                                    (Hydroxyl No. 662)                                                      9     ethylene glycol                                                                             40,000    83                                             10     1,3-propanediol                                                                             50,000    56                                             11     triethylene glycol                                                                          46,000    44                                              6     None          128,000   100                                            (control)                                                                     ______________________________________                                    

EXAMPLE 3

The general procedure of Example 1 was followed, except that no methanolwas added, the molar ratio of formaldehyde to phenol was 1.25:1 and theglycerol was replaced with a polyether triol having a hydroxyl number of662. This triol was added in an amount of 0.024 mole per mole of phenolafter the first step of the reaction had been carried out until the freeformaldehyde in the reaction mixture was reduced to 10% by weight of themixture. The final stage of the reaction was carried out until the freeformaldehyde was about 0.1% by weight of the resin. The viscosity ofthis resin was 1,280,000 cps at 25° C. A control resin prepared in thesafe manner without the addition of polyether triol had a viscosity ofgreater than 2,000,000 cps. This indicates that the process of thisinvention can be carried out using resins which do not incorporate amonohydric alcohol. This example also shows that such resins preparedusing a hydroxy compound which contains two or more hydroxy groups permolecule gives a resin with considerably lower viscosity than a controlprepared without the use of a hydroxy compound.

EXAMPLE 4

This example illustrates the use of the modified phenolic resole resinin the "no-bake" process. Solutions of various resins of Example 1 wereprepared by dissolving 65 parts of the resin and 8 parts by weight ofthe dibasic ester DBE-9 and 27 parts by weight of an aromatichydrocarbon solvent containing 98% aromatics, 2% aliphatics and having adistillation range of 55°-173° C. Each of the solutions also contained0.4% of silane A-1160 available from the Union Carbide Corp., New York,N.Y. The isocyanate solution used for the preparation of the foundrybinder was prepared by dissolving 71% by weight of a polymethylenepolyphenyl isocyanate (M-20S, available from BASF Corporation) in anaromatic hydrocarbon solvent.

To a mixer was added 2500 g of silica sand. The mixture was started and17.2 g of the modified phenolic resole resins solution and 14.1 g of theisocyanate solution were added. Then, 0.8 ml of a 25% solution ofphenylpropylpyridine in the aromatic hydrocarbon solvent was added. Thesand was discharged from the mixer one minute after the addition of thecatalyst. The sand was used immediately to form standard AmericanFoundry Society 1-inch dogbone tensile briquets using a Dietert No. 69612-gang core box. Cores were cured at room temperature and broken after10-minute, 1-hour and 24-hour cure times. Tensile strengths weredetermined using a Detroit Testing Machine Company, Model CST Tester. Acomparative test run was made with Acme Bond No. 5044A, a commercialphenolic resin available from the Acme Resin Corporation, Westchester,Illinois. The results given in Table III indicate that the resins madeby the process of this invention which show very low free formaldehydecan be used in the "no-bake" process to give cores of satisfactorystrength comparable to those obtained using a commercial resole resin.

                  TABLE III                                                       ______________________________________                                        Cores Prepared By The No-Bake Process                                         Resin No. Used                                                                              Tensile Strength (psi)                                          In Test Cores 10 min.     1 hr.  24 hrs.                                      ______________________________________                                        1             65          235    323                                          2             75          247    298                                          3             93          248    348                                          5             97          213    333                                          Commercial resin                                                                            108         250    350                                          (comparative test)                                                            ______________________________________                                    

EXAMPLE 5

The tests described in Example 4 were repeated, using the resinsprepared in Example 2. Again, the comparative test resin was thecommercial resin 5044A of the Acme Resin Corporation. The results givenin Table IV indicate that phenolic resole resins modified with a varietyof polyhydroxy compounds are suitable for use in the "no-bake" processfor making foundry cores and molds.

                  TABLE IV                                                        ______________________________________                                        Cores Prepared By The No-Bake Process                                         Resin No. Used                                                                              Tensile Strength (psi)                                          In Test Cores 10 min.     1 hr.  24 hrs.                                      ______________________________________                                         8            118         207    345                                           9            122         260    345                                          10             80         210    330                                          11             98         213    330                                          Commercial resin                                                                            112         265    340                                          (comparative test)                                                            ______________________________________                                    

EXAMPLE 6

This example illustrates the use of the modified phenolic resole resinsin the "cold-box" process. For this process, a solution of the resin isprepared by dissolving 65 parts by weight of the resin in 8.6 parts ofdioctyladipate, 15.8 parts of aromatic hydrocarbon solvent, 8.6 parts ofdibasic ester DBE-9 and 2 parts of a release agent (a mixture of oleicacid and FLEXRICIN 100, a fatty acid available from Caschem, Bayonne,N.J.). The resin solution and isocyanate solution were mixed with sandin the same proportions as was done for the "no-bake" process in Example4. In this case, the isocyanate solution contained 75% M-20S, 6.5%kerosene, 17.85% aromatic solvent and 0.65%benzenephosphorusoxydichloride. The foundry mix was blown into a RedfordCBT-1 core blower. Cores were blown at 50 PSI air pressure and gassedfor 3 seconds with 12% dimethylethylamine in carbon dioxide at 30 psiand then for 5 seconds with purge air at 30 psi. Tensile strengths weremeasured 1 minute, 1 hour and 24 hours after curing, using the Detroittesting machine Model CST tensile tester. Comparative tests were run oncores prepared using a commercial phenolic resin solution, Acme Flow No.2014 available from the Acme Resin Corporation. The results given inTable V show that binders prepared using the modified phenolic resoleresins are suitable for use in the cold box process for making cores andmolds.

                  TABLE V                                                         ______________________________________                                        Cores Prepared By The Cold-Box Process                                        Resin No. Used                                                                              Tensile Strength (psi)                                          In Test Cores 1 min.      1 hr.  24 hrs.                                      ______________________________________                                        3             148         173    213                                          8             153         183    212                                          Commercial resin                                                                            163         198    218                                          (comparative test)                                                            ______________________________________                                    

EXAMPLE 7

The modified phenolic resole resins were also used to prepare test coresafter the mixture of sand resin and isocyanate had been held for varioustimes before they were gassed with the amine catalyst. The results givenin Table VI show that the resin mix prepared using the modified phenolicresole resins which have low free formaldehyde have bench lives that aresomewhat better than those prepared using the commercial resole resin.

                  TABLE VI                                                        ______________________________________                                        Bench Life Tests                                                              Resin No. Used                                                                            Tensile Strength (psi)*                                           In Test Cores                                                                             0 hrs.  1 hr.   2 hrs.                                                                              3 hrs. 4 hrs.                               ______________________________________                                        3           148     115     90    83     73                                   8           153     103     88    78     68                                   Commercial resin                                                                          163     105     83    58     52                                   (comparative test)                                                            ______________________________________                                         *The times in the table refer to the age of the sandresin mixture before      cores were formed. Tests were run 1 minute after gassing.                

Thus, it is apparent that there has been provided, in accordance withthe present invention, a method for preparing a modified phenolic resoleresin and a foundry binder composition that fully satisfies the objects,aims and advantages set forth above. While the invention has beendescribed in conjunction with specific embodiments thereof, it isevident that many alternatives, modifications and variations will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, it is intended to include all suchalternatives, modifications and variations as set forth within thespirit and scope of the appended claims.

What is claimed is:
 1. A binder composition comprising a mixture of aphenolic resin component, an isocyanate component selected fromdiisocyanates and polyisocyanates and sufficient catalyst to causesubstantially complete reaction between the phenolic resin component andthe isocyanate component, wherein the phenolic resin component is aphenolic resole resin wherein the preponderance of the bridges joiningthe phenolic nuclei are ortho-ortho benzylic ether bridges and which hascovalently bound into the resin an aliphatic hydroxy compound whichcontains two or more hydroxy groups per molecule and has a hydroxylnumber of from about 200 to about 1850, the molar ratio of the hydroxycompound to the phenol being from abut 0.001:1 to about 0.03:1.
 2. Thebinder composition of claim 1, wherein the aliphatic hydroxy compoundwhich contains two or more hydroxy groups per molecule is selected fromthe group consisting of ethylene glycol, propylene glycol,1,3-propanediol, diethylene glycol, triethylene glycol, glycerol,sorbitol and polyether polyols having a hydroxy number from about 200 toabout
 1850. 3. The binder composition of claim 1, wherein the phenolicresole resin is prepared from unsubstituted phenol and formaldehyde. 4.The binder composition of claim 1, wherein the isocyanate component ispolymethylene polyphenylisocyante.
 5. A binder composition comprising amixture of a phenolic resin component, an isocyanate component selectedfrom diisocyanates and polyisocyanates and sufficient catalyst to causesubstantially complete reaction between the phenolic resin component andthe isocyanate component, wherein the phenolic resin component is analkoxy-modified phenolic resole resin wherein the preponderance of thebridges joining the phenolic nuclei are ortho-ortho benzylic etherbridges and which has covalently bound into the resin an aliphatichydroxy compound which contains two or more hydroxy groups per moleculeand has a hydroxyl number of from about 200 to about 1850, the molarratio of the hydroxy compound to the phenol being from about 0.001:1 toabout 0.03:1.
 6. The binder composition of claim 5, wherein the alkoxygroup is a methoxy group.
 7. The binder composition of claim 5, whereinthe aliphatic hydroxy compound witch contains two or more hydroxy groupsper molecule is selected from the group consisting of ethylene glycol,propylene glycol, 1,3-propanediol, diethylene glycol, triethyleneglycol, glycerol, sorbitol and polyether polyols having a hydroxy numberfrom about 200 to about
 1850. 8. The binder composition of claim 5,wherein the modified phenolic resole resin is prepared fromunsubstituted phenol and formaldehyde.
 9. The binder composition ofclaim 5, wherein the isocyanate component is polymethylenepolyphenylisocyante.